1. Field of the Invention
The present invention is directed to an antenna for distributed wireless communications systems. More particularly, the antenna is configured as a modified log-spiral antenna and can be utilized in a network that provides in-building wireless (IBW) communications.
2. Background
Several hundred million multiple dwelling units (MDUs) exist globally, which are inhabited by about one third of the world's population. Better wireless communication coverage is needed to provide the desired bandwidth to an increasing number of customers. Thus, in addition to new deployments of traditional, large “macro” cell sites, there is a need to expand the number of “micro” cell sites (sites within structures, such as office buildings, schools, hospitals, and residential units). In-Building Wireless (IBW) Distributed Antenna Systems (DASs) are utilized to improve wireless coverage within buildings and related structures. Conventional DASs use strategically placed antennas or leaky coaxial cable (leaky coax) throughout a building to accommodate radio frequency (RF) signals in the 400 MHz to 6 GHz frequency range.
In recent years, consumers have demanded high rates from mobiles devices. Emerging high speed cellular and wireless technologies such as 3G, WiMax, WiFi, and LTE have promised and are delivering mobile broadband wireless connectivity. As a result, consumers are substituting landlines for mobile phones, and are expecting uninterrupted coverage from the wireless services providers. Since more than half of all mobile communications now originate from inside building, the way wireless services providers plan their networks for coverage and capacity is rapidly changing. The increase in data rate with finite transmit power will lead to cells with smaller radii. This trend will lead to a rapid development and deployment of Distributed Antenna Systems (DAS), both indoors and outdoors.
A large part of the deployment cost for an indoor DAS for an IBW system is the labor to install and upgrade the wireless cabling and hardware. Thus, a need exists for a low cost and easy to install and upgrade structured cabling transmission system. Located below the ceiling, the structured cabling system will distribute wired (via an enterprise grade Passive Optical Network (PON)) and wireless signals (Cellular, PCS, Telemetry, WiFi, Public Safety). One such system is described in co-pending US Publication Nos. 2012-0293390 and 2012-0295486. Key components of this structured cabling system include broadband antennas that are easily attached to the structured cabling solution; either directly to the cable or to the remote radio unit. Current IBW DAS deployment employs multiple discrete antennas whereby one antenna is used for each service: one antenna for Public Safety, one antenna for WiFi, and so on.
Physical and aesthetic challenges exist in providing IBW cabling for different wireless network architectures, especially in older buildings and structures. These challenges include gaining building access, limited distribution space in riser closets, and space for cable routing and management.
Outside the United States, carriers are required by law in some countries to extend wireless coverage inside buildings. In the United States, bandwidth demands and safety concerns will drive IBW applications, particularly as the world moves to current 4G architectures and beyond.